Interdental brushes have been in use for a considerable length of time. Among early contributions to the body of prior art is U.S. Pat. No. 4,691,404. The interdental brush disclosed therein comprises a brush part consisting of bristles secured to a spine of twisted metal wires. The spine is embedded in a handle made of a mixture of a thermoplastic elastomer and a polypropylene material. The brush part is fastened to the handle by means of in-situ injection moulding of the handle onto the spine of the brush part.
An alternative way of securing the spine of the brush part to the handle is known from interdental brushes on the market. Here, the handle is not moulded in-situ onto the spine of the brush part. Instead, the handle of a relatively rigid polymer material, such as polypropylene, consists of two halves, each of which is formed separately, typically by means of injection moulding. The halves are fastened to each other with the spine of the brush part secured between them. A similar concept is shown in JP-A-2003-250633. JP-Y-04-46576 discloses an interdental brush with a twisted wire brush and a handle made of a relatively hard or rigid plastic. At an end of the handle, where the spine of the twisted wire brush protrudes, there is provided a substantially cylindrical recess. The recess is filled with a body of a soft, rubber-like material. The spine of the twisted wire brush extends through the body of rubber-like material and is embedded in the plastic handle. The point of this rubber-like body is that when the brush part during use is redirected at an angle relative to the longitudinal axis of the handle, the spine is not bent sharply at one single point. Instead, it is bent smoothly along a longer part of the spine inside the rubber-like body. This reduces the metal fatigue of the spine and hence increases the life-span of the interdental brush.
WO-A-01-34058 suggests an interdental brush with a brush part, a twisted wire spine of which is embedded in a main body of a handle made of a relatively hard or rigid plastic. At a front end of the handle, where the twisted wire spine of the brush part protrudes, there is provided a surface layer of a soft, elastomeric material. The elastomeric surface layer has a supposed cushioning effect, such that the gums are not hurt or damaged when the front end of the handle is accidentally pushed against them during use. A method of manufacture is suggested where the elastomeric material is in-situ moulded onto the hard plastics and the spine. A similar concept is shown in JP-Y-04-46577.
JP-A-09-168426 discloses an interdental brush which comprises a wire brush, a handle body of a hard synthetic resin, and a deformable member of a soft synthetic resin. This deformable member has one end embedded in the handle body, while the other end projects from the handle body. The spine of the wire brush extends through the deformable member of soft synthetic resin and is embedded in the handle body. A method of manufacturing is also suggested, in which the handle body is moulded in-situ onto a combined body comprising the wire brush and the deformable member of soft synthetic resin. However, the soft member of this prior-art brush has insufficient cushioning effect.
Further examples of interdental brushes are disclosed in CA-A-2,545,264 and U.S. Pat. No. 5,435,033. The interdental brushes disclosed in these two documents have no cushioning effect at all.